<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>margin样式</title>
    <style>
        .father {
            width: 500px;
            height: 500px;
            background-color: pink;
            /*border-top: 1px solid transparent;*/
            /*padding-top: 1px;*/
            overflow: hidden;

        }

        .son {
            width: 200px;
            height: 200px;
            background-color: purple;
            margin-top: 100px;
        }
    </style>
</head>
<body>
<div class="father">
    <div class="son"></div>
</div>
</body>
</html>